B7 is the standard diesel sold at every UK pump - up to 7% biodiesel, and every diesel car on the road takes it. "SDV" and similar premium-diesel labels are the higher tier: more cetane, more detergent, and a measured 17.2p a litre more expensive than standard B7 across the forecourts publishing both. For most diesel drivers it is an occasional treatment, not a diet.
- B7 means up to 7% renewable biodiesel in standard fossil diesel; it is the UK norm.
- Every diesel vehicle sold in the UK is B7-compatible - no decision to make at the pump.
- Premium diesel averages 17.2p a litre more than standard, measured at the pump.
- Diesel itself averages 182.4p a litre, up over 40p on the year.
Decoding the diesel pump
While petrol drivers choose between E10 and E5, diesel drivers meet their own set of acronyms at the forecourt: B7 on the standard pump, and a variety of premium badges beside it. Understanding what they mean matters less for compatibility - all standard diesel is B7 - and more for deciding whether the premium tier is worth paying for.
What is B7 diesel?
B7 is the standard grade of diesel sold across the UK. The "B" stands for biodiesel and the "7" indicates it contains up to 7% renewable biodiesel (FAME - fatty acid methyl ester) mixed with fossil diesel. The blend reduces the fuel's overall carbon footprint without requiring engine modifications.
Every diesel car sold in the UK is fully compatible with B7, and it has been the standard for years - when you search for standard diesel on FindPetrol, you are searching B7 prices. The specification it must meet is BS EN 590, which also governs properties like cold-weather performance, so UK winter diesel is already blended for the climate.
What is the premium tier?
Sold as "premium diesel", "ultimate diesel" and various brand names, the higher tier is still fundamentally a B7-style road diesel with two upgrades: a higher cetane rating and a concentrated detergent package.
A higher cetane number means the fuel ignites faster and more completely in the cylinder, giving smoother running, a quieter engine and marginally better cold starting. The detergents target injector and combustion-chamber deposits, and by extension the Diesel Particulate Filter - the DPF that punishes diesel cars used mainly for short city trips, where soot builds and regeneration never completes.
Is premium diesel worth it?
The honest answer is the same as for premium petrol: the chemistry works, the price is the question. We measure the gap directly - across every forecourt publishing both a standard and a premium diesel price, the premium averages 17.2p a litre more:
| Fill size | Extra at 17.2p a litre | Per year at one fill a week |
|---|---|---|
| 50 litres | £8.60 | £447.20 |
| 60 litres | £10.32 | £536.64 |
| 70 litres (van) | £12.04 | £626.08 |
Running premium diesel permanently is hard to justify on those numbers: the economy gain in an engine designed for standard B7 is small. The case that does hold up is occasional - a tank of the good stuff every month or two as a detergent treatment for a car whose trips are mostly short and urban, where DPF health is the real expense at stake. That is the same logic as our premium petrol cleaning guide, and it costs about £1.08 a tank amortised at one-in-eight frequency.
The year diesel just had
Context worth knowing while standing at the diesel pump: standard diesel currently averages 182.4p a litre, against 161.2p for petrol. Twelve months ago the diesel-petrol gap was under 8p; it now stands at 21.3p. Diesel has absorbed roughly 40p a litre of increases over the year, against about 27p for petrol. Why that happened - and why the pump lags the barrel - is covered in our fuel prices guide; what it means for choosing between a petrol and a diesel car is in petrol versus diesel running costs.
One practical note for winter
B7's FAME content is the component that ages: standing fuel can pick up moisture and bugs grow at the fuel-water interface in long storage. For a diesel that sits over winter - a van laid up, a motorhome - a diesel-specific stabiliser and a full tank are cheap insurance. For a car in daily use it is a non-issue. The full cold-weather routine is in our winter driving guide.
Checking diesel prices near you
Whatever you drive, the price you pay depends far more on which forecourt you use than on anything else. Diesel currently averages 182.4p a litre across the 7,986 stations we track, and the spread between the cheapest and dearest in a single town is worth several pounds on a full tank - for a worked example, see current petrol prices in Glasgow. Search your postcode to see diesel prices near me ranked cheapest first, or browse fuel prices by area to see how your town compares.
Frequently asked questions
Can I use B7 in any diesel car?
Yes. It is the UK standard and every diesel vehicle sold here is designed for it, including those with DPFs.
Does premium diesel give better mpg?
In an engine designed for standard diesel, the economy gain is small - typically too small to pay for the 17.2p premium. The detergent and DPF benefits are the real reason to run it occasionally.
Is B7 the same as HVO?
No. HVO is a paraffinic renewable diesel sold as a drop-in alternative at some forecourts, chemically different from the FAME biodiesel in B7. It is not the standard pump grade.
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